The Conservative leadership is threatening to send written cautions to Tory MPs who sought to undermine Iain Duncan Smith during this week's party conference.
Mr Duncan Smith admitted there are "malcontents" within his party
The Chief Whip, David Maclean, plans to interview those suspected of briefing against Mr Duncan Smith during the conference in Blackpool.
If he is not satisfied with their explanation, he will write to them and their constituency parties, issuing a warning about their future behaviour.
The development comes after Mr Duncan Smith dismissed challenges to his position as "froth and nonsense" that would blow away.
Mr Maclean's "highly unusual" decision to threaten MPs with written warnings indicates the anger felt at the way the Conservative Party conference was overshadowed by talk of a leadership challenge, says BBC political correspondent Shaun Ley.
But senior party officials say the behaviour of some MPs undermined not only Mr Duncan Smith but the party.
The former shadow foreign secretary John Maples is among the fewer than 10 MPs who will be summoned before the Chief Whip next week.
He has denied being involved in any plot, and described the summons as "outrageous".
The MPs will be asked if they have been collecting signatures for a leadership challenge or briefing against their leader.
Although no formal disciplinary action is being threatened, copying a warning letter to an MP's local association does represent an attempt to bring the rebels to heel, our correspondent says.
It is local Tory parties who decide whether or not their MPs are allowed to stand again at the next election.
The chairman of Mr Maples' Stratford-on-Avon constituency association, Les Topham, praised Mr Duncan Smith's conference speech.
"He explained exactly what he was going to do and providing he does it good luck to him and I am proud of him," he told BBC Radio 4's Today programme.
"I voted for Mr Duncan Smith and I will stick by him and I am quite confident John feels the same."
But Rod Reed, chairman of the Beckenham association and a long-standing critic of Mr Duncan Smith, predicted the leader could still be toppled.
"I am not necessarily saying this is desirable, but I think it is quite likely that there will be a challenge mounted next week," he told Today.
Former foreign secretary Sir Malcolm Rifkind said the Tory leader was entitled
to be "pretty fed up" at the way the plot had overshadowed the Blackpool conference.
'Ill advised' attack
On Friday Mr Duncan Smith accepted there were "some malcontents" plotting against his leadership, but said these would be dealt with by Mr Maclean.
He insisted he would take his party into the next election.
Meanwhile a Sunday Telegraph report makes allegations about the running of the Tory leader's office where his wife Betsy was employed for some months after her husband was elected leader of the party.
The newspaper claims a dossier on the allegations has been sent to the parliamentary standards commissioner.
Mr Duncan Smith has strongly denied any wrongdoing.
He threatened to sue anyone making allegations when the story first began to circulate last weekend.
Earlier the Tory leader stood by his conference speech attack on the prime minister that he lied over his role in the public naming of weapons expert Dr David Kelly.
Mr Duncan Smith said he believed Tony Blair "at any stage could have stopped" the outing of Dr Kelly's identity into the public domain.
But Jonathan Steel, of Beaconsfield Conservative Association, condemned the "desperate" and "ill-advised" attack on Mr Blair.
Mr Steel told the BBC Radio 4's World at One programme the speech was "much better than we might have feared" but still "drove me into despair".
"To use words like corrupt and liar in terms of the leader of our country is absolutely inappropriate and I think it is overstepping the bounds of what is acceptable in politics and amongst gentlemen".
A total of 25 MPs would be needed to trigger a vote of confidence against Mr Duncan Smith.